Automatic rifle

ABSTRACT

An automatic rifle is disclosed, of the type which exploits the pressure of the explosion gases for cocking the bolt, the improvement consisting in a simplified arrangement for the guiding tube in which the gas-actuated plunger or piston is slidably housed. A limited number of component parts ensures a longer service life for the rifle and the assembling and disassembling operations are considerably facilitated. An improved sighting arrangement is also disclosed.

I Umted States Patent 1151 3,675,534

Beretta 51 July 11, 1972 541 AUTOMATIC RIFLE 3,432,955 3/1969 Vartanian et al. ..42/16 A 3,3l8,l92 5/1967 Miller et al 89/185 X [72] Inventor. Pier Carlo Beretta, Gardone Val Trompia, 933,098 9/1909 Mcclean I i "89,135 x 1,051,791 1/1913 Warner ......153/5s R [731 Assignee: Fabbrica D'Armi P. Beretta s.p.A.. Gar- 2 3:1 2; 5:323 F S V ee 1 mmpa (Bresca) My 3,l56,992 11/1964 Beretta ..42/1 F [22] Filed: April 21, 1970 2,881,547 4/1959 Butler 42/16 A [2] 1 Appl' 3o492 Primary Examiner-Stephen C. Bentley Attorney-Shlesinger, Fitzsimmons & Shlesinger 3O Forei n A lication Prlorit Data l 8 PP 57 ABSTRACT A 129,1969 Ital ..l62l2A69 p" y I An automatic rifle is disclosed, of the type which exploits the pressure of the explosion gases for cocking the bolt, the im- [5 2] 5 k 1 5 provcment consisting in a simplified arrangement for the guid- I 9/ ing tube in which the gas-actuated plunger or piston is slidably [5]] hit. Cl ..F4ld 5/04 housed A limited number of Component parts ensures a [58] held oi Search ..33/5358;42/l F, longer service lif f m ifl and h assembling and disas- 42/16 17 39/135- I92, sembling operations are considerably facilitated. An improved sighting arrangement is also disclosed. [56] References Cited 3 Claims, l5 Drawing Figures PATENTEDJUL 1 1 I972 SHEET 18F 5 Hi I" arla INVENTOR AUTOMATIC RIFLE This invention relates to an improved automatic rifle which uses a portion of the explosion gases to open the receiver.

Automatic rifles are already known, in which a portion of the gases set free by the explosion is drawn from the barrel and sent to act upon a plunger-like member which brings the bolt back, causing the opening of the receiver and the subsequent ejection of the spent shell, a new cartridge being then automatically loaded into the receiver block. In such rifles. however, one of the most serious drawbacks, in general, is that one can never be absolutely sure that the opening of the receiver occurs only after the fired bullet has left the barrel, and that the explosion gases may not fire back against the shooter. In addition, in such prior art approaches, the mechanical con nection between the bolt and the bolt-operating rod is intricate and the overhauling and reassembling operations, even for the mere upkeep of the weapon, are time-consuming and cumbersome.

The principal object of the present invention is to provide, in an automatic rifle, in which the bolt-cocking operation is performed by a partial intake of the explosion gases, a simple and reliable connection between the bolt-operating rod and the carrier which, in turn, controls the movement of the bolt. Another object is to provide a connection which permits also the manual actuation of the bolt to open the receiver.

A further object is to ensure a preselected delay time in the automatic opening of the receiver immediately after a shot has been fired.

An additional object of the present invention is to provide a simple and efficient aiming device for an automatic rifle having means for a partial intake of the explosion gases.

These objects are achieved by the automatic rifle according to the invention, of the kind comprising a barrel having an explosion chamber at one end, which is adapted to be closed by a breech-bolt, and, at the opposite end, an explosion-gas intake, and which has a guiding tube mounted parallel, of said barrel and communicating at its front end with said gas intake, an operating rod slidable in the interior of said guiding tube and whose rear end has a transverse coupling groove, a compression spring mounted about said operating rod and urging the latter against the gas intake port, a carrier slidable in the receiver on longitudinal rigid ways and having a longitudinal through-bore adapted to receive the rear end of the operating rod, a locking-slider adapted rigidly to connect the operating rod to the carrier, said locking slider projecting laterally from the receiver and being retained in its locked position by a resiliently biassed lever, a receiver-bolt slidable in said breech and having an upwardly projecting pin, said carriage having in its bottom surface a slot whose axis is not rectilinear, which is adapted to be engaged by said projecting pin of said bolt, the later having on its front surface two latching dogs adapted to engage, by longitudinal sliding movement and subsequent rotation, a groove formed internally of the front portion of the receiver and extending through an arcuate portion of the cross-section of the receiver, and a firing pin housed in an axial through bore of said bolt, the rear end of the firing pin having a projecting edge adapted to be engaged by a transversely oriented pin integral with said carrier.

The outstanding advantage of the structure described above is the connection between the operating rod and the carrier, which, for overhauling, only requires that the lever be pressed, the locking slider withdrawn and the rod rotated through a small arc to disengage the pin from the groove formed in the receiver.

Another significant advantage of the rifle according to the present invention lies in that the carrier has now a considerable mass, so that it behaves like an inertial flywheel and ensures that the bullet has definitely left the barrel before the bolt may initiate the receiver-opening motion, irrespective of the so-called force" of the propelling charge of the cartridge which has been fired.

Yet another advantage is the simple and sturdy structure of the several component parts, which ensure a much longer service life of the rifle.

Other objects and advantages of the present invention will become more clearly apparent from the ensuing description, given by way of example only and without limitation, as aided by the accompanying drawings, wherein:

FIG. I is a side-elevational view, partly in cross-section, and incomplete, of the automatic rifle according to this invention.

FIG. 2 is a cross-sectional view, on an enlarged scale as compared with FIG. I, of the mechanical connection between the operating rod and the carrier-bolt assembly.

FIG. 3 is a plan view, sectioned along the line III-III in FIG. 2.

FIG. 4 is a cross-sectional view taken along the line IVIV of FIG. 2.

FIG. 5 is a cross-sectional view taken along the line V-V of FIG. 2.

FIG. 6 is a detail view, fragmentary and in cross-section, taken along the line VI-VI of FIG. 3.

FIG. 7 is a view, similar to FIG. 3, along the line VlI--Vll of FIG. 2, with but the carrier shown in an intermediate stage of the receiver-opening stroke.

FIG. 8 is a view similar to FIG. 7, in which the carrier-andbolt assembly is at the end of the receiver-opening stroke.

FIG. 9 is a cross-sectional view, taken along the line IXIX of FIG. 8.

FIG. 10 is a longitudinal cross-sectional view taken along the line X-X of FIG. 9.

FIGS. 11 and 12 are detail views, in plan and side elevation, respectively, of an alternative embodiment of the bolt.

FIG. 13 is a front view of the aiming assembly.

FIG. 14 is a side view of the device of FIG. 13, and

FIG. I5 is a partial cross-sectional view taken along the line XV-XV of FIG. 14.

Having now reference, at the outset, to FIG. 1, the automatic rifle according to the present invention comprises a barrel 10 which forms an explosion chamber II, a receiver 12 carrying the reloading and tiring mechanism, the grip I3, the trigger 14, the automatic magazine 15 and the aiming assembly I6. The rifle butt is affixed, in an appropriate manner (not shown) to the receiver 12.

The barrel 10 has, near its front end, a gas-intake port I7, through which a portion of the explosion gases is drawn.

Parallel to the barrel I0 a guiding tube 18 is mounted thereover, which communicates, near its own from end, with the gas-intake port 17. In the interior of the tube I8 is slidably housed a plunger 19 having a stem 20 and urged by a spring 21 towards the right as viewed in FIG. 1.

The stem 20 has, at its rear end, a radially projecting pin 22 and (FIG. 2) has a transverse groove 23. The front portion of the receiver I2 has a lowermost tapped hole 24 into which the barrel I0 is screwably affixed, and an uppermost bore 25 which offers a seat to the rear end of the guiding tube I8, which abuts an annular abutment 26 (see FIG. 10), having a longitudinal groove 27 which is adapted to allow a sliding motion for the pin 22 during the insertion of the stem 20 into the receiver. In registry with the end of the barrel 10, the receiver 12 has an outwardly radially protruding step 28 which extends along a partial arc along the receiver section, a longitudinal groove 29 being interposed for a purpose to be specified hereinafter.

A carrier 31 is housed in the receiver 12 so as to slide along longitudinal ways 30. The front portion of the carrier 31 has a hole 32 adapted to receive the rear end of the stem 20, and a through-opening 33 adapted to match; in transverse alignment, the opening 23 formed on the stem 20.

To lock the stem 20 to the carriage 31 a locking-slider 34 is provided, which is adapted to enter the opening 33 and the groove 23 and that has an end which projects laterally outside the receiver, the latter having, in turn, an elongate hole 12A to allow the sliding of the slider 34. To facilitate the insertion of the slider 34 into the opening 33, it has a bevelled end 35, whereas to latch it (FIG. 6) a notch 36 is provided on the slider 34, so as to give a seat to a tooth 37 of a lever 38 which slides in a groove 38A, as urged by a compression spring 39 towards the slider-latching position. As clearly shown in FIG. 6, it suffices, to set the locking slider 34 free, that the lever 38 be pulled back, by pushing upon the knurled portion 40 against the bias of the spring 39.

Through the bottom face 41 of the carriage 31 a groove 42 is formed, whose axis is not rectilinear and has, instead, the outline shown in FIG. 3. The groove 42 affords a sliding seat to a pin 44 projecting from the top surface of a bolt 45 having a central through-bore for housing a firing pin 47: the latter, as the bolt closes the receiver in the position of FIG. 2, can be driven into the explosion chamber 11.

The front portion of the bolt 45 has two lateral and diametrically opposite dogs 48 (FIG. 11) which are adapted to be retained by the step 28 of the receiver within the groove 49 formed by the step itself. As shown in FIG. 2, the rear end of the firing pin has a collar 50 and a bottom abutment 52 and a pin 51 is inserted in the carrier 31 for a purpose to be clarified hereinafter.

It is appropriate to observe that the longitudinal ways 30 are terminated in registry with the stp 28 so as to be flush, on one side, with the longitudinal groove 29 and, on the other side, with the upper edge ofthe step 28.

The operation of the rifle is as follows:

Starting from the position of FIG. 2, and assuming that a cartridge is contained in the explosion chamber 11, by actuating the trigger 14, the firing pin 47 strikes the capsule of the cartridge, so that the cartridge is fired and thrusts the bullet out of the barrel 10. Before the bullet leaves the barrel, a portion of the explosion gases is channeled though the gas intake port 17 and acts on the plunger 19: the latter is thrust backwards against the bias of the return spring 21. The operating stem or rod drives the carriage 31 backwards and the latter slides, in correspondence with the initial rectilinear portion of the groove 42, relative to the bolt 45 and then due to the engagement of the pin 44 with the second, non aligned portion of the groove 42, causes the bolt to be rotated about its own longitudinal axis to disengage the teeth 48 from the step 28 and, more particularly, it brings one tooth to match the groove 29 of the step and the other tooth to match the portion of the receiver 12 where the step 28 is lacking. At this stage, both the carrier and the bolt are in the positions as shown in FIG. 7. By so doing, the bolt 45 can slide back as controlled by the carrier 31 and thus the explosion chamber is cleared, and the bolt effects, in a manner and with the devices as known the conventional art, the ejection of the spent shell and the automatic loading of another cartridge, drawn from the magazine 15, into the chamber I]. At this stage, wherein both the carrier 31 and the bolt 45 are in the position shown in FIG. 8, the spring 21 thrusts forward the plunger 19 again and the operating rod 20 therewith. Consequently, the carrier 31 is driven forward. Inasmuch as the teeth 48 of the bolt are guided for sliding by the longitudinal ways 30, the return of the carrier also drives the bolt 45 until the latter is again with the teeth 48 in the groove 49 as formed by the step 28. At this stage, due to the sliding motion of the groove 42 relative to the pin 44, the bolt 45 is rotated about its own longitudinal axis and locked in the receiver-closing position, in readiness for firin g another cartridge.

On comparing FIGS. 2 and 7, it can be clearly seen that the firing pin 47 projects frontally from the bolt and is thus in a position to fire only when the bolt-carrier assembly is closed. Otherwise, due to the engagement of the pin 51 with it, the assembly is in retracted position with respect to the bolt and cannot project ahead of same. any possibility being thus prevented of an accidental firing before the bolt has thoroughly closed the breech. Emphasis should also be given to the fact that the groove 42 has a rectilinear initial portion so that the rotation which is necessary for clearing the bolt from the step 28 is started with a certain preselected delay relative to the beginning of the backward motion of the carrier.

Consequently, one can be assured that the bolt can open the receiver only when the bullet has left the barrel 10.

It should also be observed that the two ends of the guiding tube are equal to one another so that the tube can be reassembled without any special care over the barrel. As a matter of fact, the holes 53 for venting the explosion gases are formed at both ends of the tube 18.

In the alternative embodiment shown in FIGS. 11 and 12, the bolt 145 has a pin 144 for cooperating with the groove 142 formed in the carrier wherein the pin 144 has a polygonal outline, so that, according to which of the portions of the groove 142 is engaged by the pin, different surfaces of the pin 144 will be engaged. More particularly, observing FIG. 11, where the groove 142 has been shown in dash and dot lines, it can be seen that the groove comprises a portion 142A and a portion 142B: in the first portion there will be slidably engaged and thus subjected to forces the two opposite planar surfaces 144A of the pin 144, whereas the second portion 1428 will engage the opposite surfaces of the pin 144B. By so doing it is possible, at each carrier stroke, i.e. for each cartridge fired, to prevent the pin 144 from being stressed over the same engagement area with the groove 142, the stresses being conversely distributed around the entire contour of the pin throughout.

Referring now to FIGS. 13, 14 and 15, the aiming device 16 is shown, which is a dioptrical sighting device mounted astride the receiver 12 and comprising two side plates 61 shaped so as to encompass the top portion of the receiver and to adhere to same. At a first end, between the plates 6l, a pin 62 is mounted, on which, in an intermediate position between the plates, a lever 63 is pivotally mounted, which is terminated, at the opposite end of the aiming device, by a wing 64 having an aiming pinhole 65 formed therethrough.

As clearly shown in FIG. 14, one of the base sides 66 of the lever 63 is cut so as to receive, by resting thereover, a support 67 which is pivotally mounted between the plates 6] and is an integral part of a pin 68: the latter is terminated, on the one side, by a knurled actuating knob 69 and, at the other side, it carries a resilient locking washer 70 held in position by a plug 71.

Between the two sides 66 and 72 of the lever 63, a pin 73 is provided, which is integrally affixed to the sides and is acted upon by the end of a coil spring 74 wound about the pin 68, the opposite end of the spring engaging the front plate 75 which interconnects the side plates 61. FIG. 14 clearly shows that the spring 74 holds the lever 63 against the pin 68 and, more detailedly, the side 66 thereof against the supporting member 67. Emphasis should be given to the fact that the supporting member 67 has a polygonal, preferably triangular, cross-sectional outline, in which the planes of the sides are set at different distances from the axis of the pin 68. By so doing, according to which face of the supporting member 67 is the supporting surface for the base side of the lever 63, the latter is more or less raised with respect to the pin 68 and thus the effective firing distance range can be varied. Once the several faces have been calibrated according to the distances corresponding thereto, the calibration remains unvaried during the whole service life of the rifle.

The aiming device comprises, in addition, a back-sight leaf 76, pivoted for rotation about the pin 68 and intended for grenade throwing. The leaf 76 comprises a front plate 77 having two holes '78 and a notch 81 for aiming, and two side wings, interconnected by the plate 77, one of said wings having a projection 79 adapted to engage either recess 80 of the two formed in one of the plates 61 and which serves for retaining the portion 76 in the two positions, active and inactive, respectively, shown in solid lines and in dotted lines in FIG. 14.

It remains to emphasize the fact that, with the fastening system between the operating rod and the carrier-bolt assembly according to the present invention, the bolt can be made lighter in weight, whereas a considerably heavier mass can be attributed to the interconnecting carrier: the latter thus operates like an inertial flywheel for adjusting the opening of the receiver by the bolt.

As a matter of fact, since the carrier has a considerable mass, it immediately stores all the power set free by the explosion gases and yields it evenly for the opening stroke of the bolt, without the bolt being influenced by the different forcc of the cartridges being fired.

It should not be overlooked, in addition, that the action of the gases unfolds itself during an extremely short time and for a slight fraction of the carrier return stroke, so that the inertia of the carrier takes a considerable meaning.

It is appropriate to emphasize, lastly, that the sliding ways 30 for the carrier and the bolt dogs are also a reinforcing and stiffening member for the breech.

The invention has been described in connection with a preferred embodiment thereof, it being understood, however, that a number of modifications and changes, ideally and constructionally equivalent thereto, can be introduced therein without departing from the scope of this invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An automatic rifle comprising a barrel,

a receiver at one end of said barrel,

a guiding tube mounted parallel to said barrel,

a gas intake duct connecting the bore of said barrel with the front end of said tube,

an operating rod slidable in said guiding tube,

said tube having a plunger at its front end and a transverse coupling groove at its rear end,

a compression spring mounted about said rod and interposed between said receiver and said plunger,

a carrier slidable in said receiver on longitudinal rigid ways and having a longitudinal bore to receive the rear end of said operating rod,

a removable locking slider projecting laterally from said receiver for locking said operating rod to said carrier,

a lever for holding said slider in locked position,

resilient means constantly urging said lever into slider-holding position,

a breech bolt rotatable and slidable in said receiver and having two dogs at its front end which, upon rotation of the bolt in one direction, engage in a groove in said receiver defined by a step projecting from the internal surface of said receiver to retain said bolt locked in closed position,

said carrier having in its bottom a groove with a nonrectilinear axis which is engaged by said step,

a firing pin slidably housed in an axial bore of said bolt and having at its rear end an outwardly projecting annular edge,

and a pin mounted transversely in said carrier and positioned to engage said annular edge,

said operating rod having at its rear end a radially projecting pin positioned to engage an abutment step formed internally of said receiver,

said abutment step having a groove longitudinally oriented with respect to said receiver and disposed to allow sliding motion of said radially projecting pin therethrough, said radially-projecting pin being on the same side as said transverse coupling groove at the rear end of said rod.

2. An automatic rifle comprising a barrel,

:1 receiver at one end ofsaid barrel,

a guiding tube mounted parallel to said barrel,

a gas intake duct connecting the bore of said barrel with the front end of said tube,

an operating rod slidable in said guiding tube,

said tube having a plunger at its front end and a transverse coupling groove at its rear end,

a compression spring mounted about said rod and interposed between said receiver and said plunger,

a carrier slidable in said receiver on longitudinal rigid ways and having a longitudinal bore to receive the rear end of said operating rod,

said carrier having in its bottom a groove with a nonrectilinear axis which is engaged by said step,

a firing pin slidably housed in an axial bore of said bolt and having at its rear end an outwardly projecting annular edge,

and a pin mounted transversely in said carrier and positioned to engage said annular edge,

said carrier having a transverse opening aligned with said transverse groove of said operating rod and forming a seat for said locking slider, said locking slider having a front bevel which facilitates its introduction into said opening, and

said slider having a lateral groove therein,

a lever having a latching tooth which slides in said lateral groove ofsaid slider and in a groove in said carrier, and

a compression spring constantly urging said latching tooth toward latching position,

said lever having an external knurled surface for manipulation.

3. An automatic rifle comprising a barrel,

a receiver at one end of said barrel,

a guiding tube mounted parallel to said barrel,

a gas intake duct connecting the bore of said barrel with the front end of said tube,

an operating rod slidable in said guiding tube,

a removable locking slider projecting laterally from said receiver for locking said operating rod to said carrier,

a lever for holding said slider in locked position,

resilient means constantly urging said lever into slider-holding position,

a breech bolt rotatable and slidable in said receiver and having two dogs at its front end which, upon rotation of the bolt in one direction, engage in a groove in said receiver defined by a step projecting from the internal surface of said receiver to retain said bolt locked in closed position,

said tube having a plunger at its front end and a transverse coupling groove at its rear end,

a compression spring mounted about said rod and interposed between said receiver and said plunger,

a carrier slidable in said receiver on longitudinal rigid ways and having a longitudinal bore to receive the rear end of said operating rod,

a removable locking slider projecting laterally from said receiver for locking said operating rod to said carrier,

a lever for holding said slider in locked position,

resilient means constantly urging said lever into slider-holding position,

a breech bolt rotatable and slidable in said receiver and having to dogs at its front end which, upon rotation of the bolt in one direction, engage in a groove in said receiver defined by a step projecting from the internal surface of said receiver to retain said bolt locked in closed position,

said carrier having in its bottom a groove with a nonrectilinear axis which is engaged by said step,

a firing pin slidably housed in an axial bore of said bolt and having at its rear end an outwardly projecting annular edge,

and a pin mounted transversely in said carrier and positioned to engage said annular edge,

and an aiming device comprising two lateral plates encompassing the upper portion of said receiver,

a profiled lever pivoted to rotate in a vertical plane with respect to said lateral plates and carrying an aiming hole,

a supporting member for said lever mounted rotatably between said lateral plates and having a plurality of surfaces which are at different distances from the axis of rotation of said supporting member,

a spring constantly biasing said profiled lever to rest against said supporting member, and

a backsight leaf pivoted to said supporting member for grenade throwing and rotatable between an active and an idle position. 

1. An automatic rifle comprising a barrel, a receiver at one end of said barrel, a guiding tube mounted parallel to said barrel, a gas intake duct connecting the bore of said barrel with the front end of said tube, an operating rod slidable in said guiding tube, said tube having a plunger at its front end and a transverse coupling groove at its rear end, a compression spring mounted about said rod and interposed between said receiver and said plunger, a carrier slidable in said receiver on longitudinal rigid ways and having a longitudinal bore to receive the rear end of said operating rod, a removable locking slider projecting laterally from said receiver for locking said operating rod to said carrieR, a lever for holding said slider in locked position, resilient means constantly urging said lever into slider-holding position, a breech bolt rotatable and slidable in said receiver and having two dogs at its front end which, upon rotation of the bolt in one direction, engage in a groove in said receiver defined by a step projecting from the internal surface of said receiver to retain said bolt locked in closed position, said carrier having in its bottom a groove with a nonrectilinear axis which is engaged by said step, a firing pin slidably housed in an axial bore of said bolt and having at its rear end an outwardly projecting annular edge, and a pin mounted transversely in said carrier and positioned to engage said annular edge, said operating rod having at its rear end a radially projecting pin positioned to engage an abutment step formed internally of said receiver, said abutment step having a groove longitudinally oriented with respect to said receiver and disposed to allow sliding motion of said radially projecting pin therethrough, said radiallyprojecting pin being on the same side as said transverse coupling groove at the rear end of said rod.
 2. An automatic rifle comprising a barrel, a receiver at one end of said barrel, a guiding tube mounted parallel to said barrel, a gas intake duct connecting the bore of said barrel with the front end of said tube, an operating rod slidable in said guiding tube, said tube having a plunger at its front end and a transverse coupling groove at its rear end, a compression spring mounted about said rod and interposed between said receiver and said plunger, a carrier slidable in said receiver on longitudinal rigid ways and having a longitudinal bore to receive the rear end of said operating rod, said carrier having in its bottom a groove with a non-rectilinear axis which is engaged by said step, a firing pin slidably housed in an axial bore of said bolt and having at its rear end an outwardly projecting annular edge, and a pin mounted transversely in said carrier and positioned to engage said annular edge, said carrier having a transverse opening aligned with said transverse groove of said operating rod and forming a seat for said locking slider, said locking slider having a front bevel which facilitates its introduction into said opening, and said slider having a lateral groove therein, a lever having a latching tooth which slides in said lateral groove of said slider and in a groove in said carrier, and a compression spring constantly urging said latching tooth toward latching position, said lever having an external knurled surface for manipulation.
 3. An automatic rifle comprising a barrel, a receiver at one end of said barrel, a guiding tube mounted parallel to said barrel, a gas intake duct connecting the bore of said barrel with the front end of said tube, an operating rod slidable in said guiding tube, said tube having a plunger at its front end and a transverse coupling groove at its rear end, a compression spring mounted about said rod and interposed between said receiver and said plunger, a carrier slidable in said receiver on longitudinal rigid ways and having a longitudinal bore to receive the rear end of said operating rod, a removable locking slider projecting laterally from said receiver for locking said operating rod to said carrier, a lever for holding said slider in locked position, resilient means constantly urging said lever into slider-holding position, a breech bolt rotatable and slidable in said receiver and having to dogs at its front end which, upon rotation of the bolt in one direction, engage in a groove in said receiver defined by a step projecting from the internal surface of said receiver to retain said bolt locked in closed position, said carrier having in its bottom a groove with a non-rectilinear axis which is engaged by said step, a fIring pin slidably housed in an axial bore of said bolt and having at its rear end an outwardly projecting annular edge, and a pin mounted transversely in said carrier and positioned to engage said annular edge, and an aiming device comprising two lateral plates encompassing the upper portion of said receiver, a profiled lever pivoted to rotate in a vertical plane with respect to said lateral plates and carrying an aiming hole, a supporting member for said lever mounted rotatably between said lateral plates and having a plurality of surfaces which are at different distances from the axis of rotation of said supporting member, a spring constantly biasing said profiled lever to rest against said supporting member, and a backsight leaf pivoted to said supporting member for grenade throwing and rotatable between an active and an idle position. 